The heart of a computer's long term memory is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider toward the surface of the disk, and when the disk rotates, air adjacent to the disk moves along with the surface of the disk. The slider flies over the surface of the disk on a cushion of this moving air. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic transitions to and reading magnetic transitions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The magnetic disk includes a magnetic media and is coated with a hard coating such as a layer of carbon, referred to as a carbon overcoat (COC). This COC is critical to maintaining the media and the magnetic head in working order. For example, the COC prevents the magnetic media from corroding and also protects the magnetic media from damage such as from contact with the slider. The COC also prevents the magnetic head from contacting the magnetic media, thereby preventing catastrophic shorting of the magnetic head as well as physical damage to the magnetic head.
Sometimes however, the COC can become compromised. For example at an asperity where the surface of the media has a bump or high point, the carbon overcoat can be worn off by contact with the slider. Over time, this causes fatal damage to the magnetic media and to the magnetic head on the slider, eventually resulting in loss of data and complete failure of the magnetic data recording system. While early detection would be beneficial to preventing such data loss and further damage to the data recording system, no method has previously existed for detecting such COC degradation at an early stage. Therefore, there remains a strong felt need for a method, system or structure that can allow such carbon overcoat (COC) degradation to be detected as soon as such degradation manifests itself.